Lubricant compositions containing terpolymers

ABSTRACT

Lubricating compositions containing a terpolymer of ethylene, with an alkyl ester of an unsaturated carboxylic acid, and with an olefinically unsaturated compound containing either a phosphorus atom or a heterocyclic nitrogen atom exhibit good thermal stability, viscosity index, and dispersant properties.

O Umted States Patent 1 [111 3,718,591 Eckert 1 Feb. 27, 1973 LUBRICANT COMPOSITIONS [56] References Cited TAININ T LYM R CON G ERPO E S UNITED STATES PATENTS [75] Inventor: Rudoli J. A. Eckert, Amsterdam,

Netherlands girliy at in [73] Assignee: Shell Oil Company, New York,N.Y. 3,030,303 4/1962 Ryan ..252/51.5X 3,192,158 6/1965 Bergstrom et a]. ..252/51.5 X [22] Flled: Jan-25,1971 3,423,367 1/1969 Merijan et a1. ..252/51.sx

21 A 1. No.: 109674 1 pp Primary ExaminerDaniel E. Wyman Related US. Application Data Assistant ExaminerW. Cannon [63] Continuation of Set. N0. 776,778, Nov. 18, 1968, Ammer'mmld Denkler abandmd' 57 ABSTRACT [30] Foreign Application Priority Data Lubricating compositions containing a terpolymer of ethylene, with an alkyl ester of an unsaturated carbox- Nov. 27, 1967 United Kmgdom ..5376l y acid, and with an olefinicany unsaturated pound containing either a phosphorus atom or a g heterocyclic nitrogen atom exhibit good thermal stal a e l e n 'l t d d t t [58] Field of Search ..2s2/49.s; 260/80 PS, 80.71 ym ex and 59mm pmper 4 Claims, No Drawings LUBRICANT COMPOSITIONS CONTAINING TERPOLYMERS This application is a continuation of application Ser. No. 776,778 filed Nov. 18, 1968, now abandoned.

This invention relates to novel lubricant compositions containing as additives polymeric compounds which, in addition to dispersant properties, also have viscosity-improving characteristics. The invention further relates to novel polymeric compounds which are suitable for use as lubricant additives.

A number of polymeric compounds have been proposed which are capable of imparting dispersant properties and improving the viscosity index of lubricating oils. A disadvantage of most of these compounds is that they possess a low thermal stability. If the lubricant in which they have been incorporated is exposed to high temperature, they are decomposed, as a result of which their favorable action is significantly reduced or disappears entirely. Therefore, when lubricants are exposed to high temperature, such as in combustion engines, it is desirable that the additives incorporated in the lubricants should possess a sufficiently high thermal stability, so that their favorable activity is retained.

A class of polymeric compounds has now been found which impart dispersant properties to a lubricating oil, improve the viscosity characteristics of the lubricating oil and possess, moreover, a very high thermal stability.

The invention therefore relates to novel lubricant compositions comprising one or more lubricants and terpolymers of one or more olefinically unsaturated hydrocarbons with one or more alkyl esters of unsaturated carboxylic acids and with one or more olefinically unsaturated compounds containing either a phosphorus atom or a heterocyclic nitrogen atom. The invention relates in particular to lubricant compositions comprising polymers selected from a class of terpolymers of olefinically unsaturated C hydrocarbons with alkyl esters of unsaturated C carboxylic acids, in which the alkyl groups contain eight-20 carbon atoms and with C olefinically unsaturated compounds containing a phosphorus atom or a heterocyclic nitrogen atom.

Terpolymers which have been found to be particularly advantageous as additives to mineral lubricating oils include the following novel compounds:

1. ethylene/lauryl methacrylate/stearyl methacrylate/diethyl iso-propylidene phosphonate terpolymer,

2. ethylene/diisooctyl itaconate/diethyl isopropylidene phosphonate terpolymer,

3. ethylene/lauryl methacrylate/stearyl methacrylate/N-vinyl-Z-pyrrolidone terpolymer,

ethylene/diisooctyl itaconate/N-vinyl-Z-pyrrolidone terpolymer,

5. ethylene/lauryl methacrylate/stearyl methacrylate/2-vinyl pyridine terpolymer.

Base oils suitable for the preparation of the lubricant compositions according to the invention are mineral lubricating oils of varying viscosity, synthetic lubricating oils or lubricating oils containing fatty oils. The present lubricant additives may also be incorporated in lubricating greases. The invention is of special importance for improving the quality of mineral lubricating oils or mixtures thereof. The polymeric compounds can be added to the lubricant as such or in the form of a concentrate obtained, for example, by mixing the polymeric compounds with a small quantity of oil. The concentration of the present polymers in the lubricant can vary between wide limits. In general, the desired dispersant action and improvement of the viscometric properties is obtained when the quantity added is from 0.1 to 10%w and in particular when this quantity is from 0.5 to 5%w of the lubricating composition.

In addition to the present polymers, the lubricant compositions according to the invention can also contain other additives, such as antioxidants, anti-corrosive agents, anti-foaming agents, agents to improve the lubricating action, and other substances which are usually added to lubricants.

The polymeric compounds incorporated into the lubricating compositions of the present invention are terpolymers of one or more olefinically unsaturated C hydrocarbons, with one or more C,, alkyl esters of C carboxylic acids and with one or more C olefinically unsaturated compounds containing either a phosphorus or a heterocyclic nitrogen atom.

The olefinically unsaturated hydrocarbons suitable for use as monomers in the preparation of the present terpolymers can be either aliphatic or aromatic hydrocarbons. Examples of suitable olefinically unsaturated aliphatic hydrocarbons are monoolefins, such as ethylene, propylene, butene and pentene, and diolefins, such as butadiene, isoprene and dimethylbutadiene. An example of a suitable olefinically unsaturated aromatic hydrocarbon is styrene. Preference is given to terpolymers which are prepared from ethylene. Terpolymers which have been prepared from diolefins may be used in lubricant compositions as such or may be hydrogenated thereby saturating at least part of the olefinically unsaturated bonds.

The alkyl esters of unsaturated carboxylic acids suitable for use as monomers in the preparation of the present terpolymers can be either alkyl esters of unsaturated monobasic carboxylic acids or alkyl esters of unsaturated polybasic carboxylic acids. Examples of suitable alkyl esters of unsaturated monobasic carboxylic acids are methyl methacrylate, isobutyl acrylate, lauryl methacrylate and stearyl methacrylate. Some examples of suitable alkyl esters of unsaturated polybasic carboxylic acids are diethyl maleate, dioctyl fumarate and diisooctyl itaconate. Preference is given to polymers prepared from alkyl esters of monobasic or dibasic carboxylic acids, the alkyl groups of which contain eight-20 carbon atoms. Particularly advantageous alkyl ester monomers are diisooctyl itaconat'e or mixtures of lauryl and stearyl methacrylates.

Examples of olefinically unsaturated compounds containing either a phosphorus atom or a heterocyclic nitrogen atom are vinyl phosphonic acid and alkyl and aryl esters thereof, isopropylidene phosphonic acid and alkyl and aryl esters thereof, such as diethyl isopropylidene phosphonate, N-vinyl-2-pyrrolidone, 2-vinyl pyridine, 4-vinyl pyridine, N-vinyl carbazole, N-vinyl- 2-oxazolidone, N-vinyl succinimide, 4-vinyl pyrimidine and 2-vinyl quinoline. Preference is given to polymers prepared from diethyl isopropylidene phosphonate or N-vinyI-Z-pyrrolidone, or 2-vinyl pyridine.

Employing the aforementioned preferred monomers, the following novel compounds have been found to be particularly advantageous in improving the viscosity,

dispersant properties and thermal stability of lubricatponents in the ratio in which they are consumed during ing oils: the reaction. The composition is kept homogeneous by l. ethylen /l ryl met y a y m h ryintensive stirring while simultaneously discharging part late/diethyl isopropylidene phosphonate terof the reaction mixture. polymer 5 The molecular weight of the terpolymers can vary 2- hyle yl i hyl i pr pybetween wide limits. The invention relates in particular lidene phosphonate terpolymer to lubricant compositions containing terpolymers with 3. ethylene/lauryl methacrylate/stearyl methacrya molecular weight (M,.) between 5,000 and 150,000, late/N-vinyl-2-pyrrolidone terpolymer more specifically to lubricant compositions containing 4. ethylene/disooctyl itaconate/N-vinyl-Z-pyrto copolymers with a molecular weight between 10,000

rolidone terpolymer and 80,000. 5. ethylene/lauryl methacrylate/stearyl methacry- The ra io of the molar Concentrations of the late/2-vinyl pyridine terpolymer. monomers can also vary within wide limits. The molar The copolymerization of olefinically unsaturated l5 ratio of the monomers in the terpolymer is generally hydrocarbons, alkyl esters of unsaturated carboxylic from 1 1 to 300 moles of olefinically unsaturated acids and olefinically unsaturated compounds containhydrocarbon to moles of alkyl esters of unsaturated ing either a phosphorus atom or a heterocyclic nitrogen eal'boxyhe acids to l to moles of the elehhicahy atom is preferably conducted in solution in the saturated p e p f or nitrogen cohtehhhg h presence f a f radical initiator, Such as an an The inventlon will now be further described with the pound or a peroxide aid of the following examples.

The ratio in which the monomers are incorporated into a growing polymer molecule depends on the reac- EXAMPLE I tivity of the monomers involved. If there are differences in reactivity, the molar ratio of the monomers in the mixture to be polymerized will be subject to considerable changes as the copolymerization proceeds, since the more reactive monomer is incorporated more rapidly. As a result, the composition of the copolymer also changes continually. As a general rule it may be said that, if in the copolymerization of monomers which differ strongly in reactivity no special measures are taken, the products obtained are of an extremely heterogeneous composition. Such a case arises in the copolymerization of olefinically unsaturated hydrocarbons, alkyl esters of unsaturated carboxylic acids and olefinically unsaturated compounds containing either a phosphorus atom or a heterocyclic nitrogen atom, isopropylidene phosphonate, and terpolymers of Sihce three (W of monomers are t h which dimethylbutadiene, stearyl and lauryl methacrylates, differ in reactivlty. In the copolymerization of these and N viny| 2 pyrrolidone Four terpolymers of ethylene, lauryl methacrylate, stearyl methacrylate and N-vinyl-2-pyrrolidone, two terpolymers of ethylene, diisooctyl itaconate and N- vinyl-2-pyrrolidone, four terpolymers of ethylene, lauryl methacrylate, stearyl methacrylate and 2-vinyl pyridine, two terpolymers of ethylene, diisooctyl itaconate and diethyl isopropylidene phosphonate and three terpolymers of ethylene, lauryl methacrylate, stearyl methacrylate and diethyl isopropylidene phosphonate, were prepared using the procedure 35 described below (polymers 1 to 15 incl.). Other compositions illustrative of the invention are terpolymers of styrene, diisooctyl itaconate and 2-vinyl pyridine; terpolymers of butadiene, diisooctyl itaconate and monomers it has been found that despite the Very A mixture of alkyl esters of unsaturated carboxylic fereht reactivity it is Possible to P p copolymers acids, olefinically unsaturated compounds containing a with a constant average composition, if care is taken phosphorus atom or a heterocyclic nitrogen atom that the ratio between the concentrations of the azodiisobutyronitrile and 400 gof benzene was passed monomers in the mixture remains constant during the into a 2-liter autoclave. After the air had been expelled copolymerization This can be accomplished y adding from the autoclave with the aid of pure nitrogen, additional quantities of the more reactive monomers or h l was i d d i h autoclave at 00111 a mixture of monomers rich in reactive monomers to temperature under a pressure of up to 170 to 200 aim the mixture being polymerized. This method is known Th mixture was h d at 65C f a certain i d, as programmed copolymerization. It is also possible to d i hi h h pressure increased to 400-500 t stop the polymerization when e Concentrations of the After the pressure had been released, the mixture was monomers in the mixture to be polymerized are ubdischarged and concentrated by partial evaporation of stantially the same. This is called copolymerization to the solvent. The polymer was purified by precipitating low conversion. three times in methanol. Finally the polymer was dis- The copolymerization of the present monomers may solved in benzene, the solution filtered and the polymer be conducted either batchwise or continuously. Conseparated by freeze-drying.

tinuous polymerization may take place in a tubular Further data on the copolymerizations and the reactor or by continuously adding the reaction comresulting terpolymers are given in Tablesland II.

TABLE I Polymer N0 l 2 3 4 5 t! 7 8 J 10 ll 1.! l5 l1 15 Quantity of monomer in tho mixture to ho polymornliosnhonnlu TABLE I Conlinucd Polymer No 1 .3 3 4 5 7 8 l l0 11 12 13 14 v 15 Quantity 01 azodiisobutyro nitrile in the mixture to be polymerized, g 0.2 0. 2 0. 15 0. 12 0. 16 0. 12 0. 12 0. 18 0. l8 0. 18 0.15 0. 15 0. 2 U, 2 0, 2 Duration of copolym on, h 3 2. 3 3 3 3 3 3. 5 3 4 4 4 3 3 3 Yield of copolymer, g 21. 7 26. 7 8. 0 1.4 21.4 13. 3 2.3 2. 6 3.1 2. 1 7. 6 J. 6 8. I 11. ll 17. 0 Average molecular weight 01 v the terpolymcrs (M||) 44, 500 34, 500 28, 000 24, 100 18,500 18. 500 16, 006 8, 250 16, 200 15, 900 32, 500 21, 800 28, 500 36, 000 12, 801) TABLE ll Molar ratio of tho monomers 1n terpolymer Lauryl Stcnryl 4 Diothyl lso- Nitrogen Phosphorus mothnrmothao- Qilsooctyl N-v1nyl-2 2-vlny1 propylidono content, content, Polymer No. rylatc rylato ltaconato pyrrolidono pyridine phosphonato Ethylene wt. percent wt. percent EXAMPLE II In order to assess their viscometric behavior, polymers lof Example I were dissolved in a concentration of 1.5%w in a paraftinic base oil. The results of the viscometric determinations are listed in Table 111.

Table III cS cS VI VT Base oil 57.77 7.36 96 Base oil 1.5% polymer 1 79.69 9.97 113 93 Base oil 1.5% polymer 2 75.53 9.50 111 94 Base oil 1.5% polymer 3 76.27 9.55 111 92 Base oil 1.5% polymer 4 77.71 9.70 l 11 92 Base oil 1.5% polymer 5 66.44 8.39 104 92 Base oil 1.5% polymer 6 70.78 8.88 107 91 Base oil 1.5% polymer 7 68.56 8.64 106 92 Base oil 1.5% polymer 8 72.10 8.96 107 87 Base oil 1.5% polymer 9 71.51 8.86 106 85 Base oil 1.5% polymer 10 70.45 8.76 105 86 Base oil 1.5% polymer 11 84.90 10.43 112 88 Base oil 1.5% polymer 12 75.82 9.42 109 89 Base oil 1.5% polymer 13 78.86 9.78 111 90 Base oil 1.5% polymer 14 75.23 9.39 110 91 Base oil 1.5% polymer 66.55 8.39 104 91 The results shown in Table 11] indicate that the polymers of the present invention are very effective in improving the viscosity index of the paraffinic base oil.

EXAMPLE Ill The thermal stabilities of the polymers according to the invention are recorded in Table IV. They were determined in vacuum at a rate of heating of 3C/min. The values T T and T represent the temperatures at which 10, 20 and 50 percent weight loss, respectively, of the polymer was attained.

To test the present polymers as dispersants they were subjected to a peptization test. In this test the lowest concentration of additive is determined that is capable of keeping 0.015%w of carbon in mineral oil in suspension for 15 minutes at 250C. The results of these peptization tests are also listed in Table IV. These results show that all the polymers tested had a significant activity as dispersants. (Values of less than 0.05 reflect good dispersancy.)

Table IV Polymer T T T Peptimtiqon Test,

The foregoing data clearly establish that the polymeric additives of the present invention impart good dispersant properties and improve the viscosity index of lubricating oils and also improve the thermal stability of the lubricant composition.

1 claim as my invention:

1. A lubricating composition consisting essentially of a major amount of a mineral lubricating oil and from 0.1 to 10 percent by weight of an oil soluble terpolymer of 1) ethylene with (2) a C alkyl ester of a C unsaturated carboxylic acid; and with (3) an alkyl ester of a C olefinically unsaturated phosphonic acid, wherein the molecular ratios of said monomers is l l-300 moles of ethylene to 10 moles of the C alkyl ester of a C unsaturated carboxylic acid to 1-15 moles of the alkyl ester of a C olefinically unsaturated phosphonic acid, said terpolymer having a molecular weight of from 5,000 to 150,000.

2. The composition of claim 1 wherein the olefinically unsaturated phosphorus compound is diethyl isopropylidene phosphonate.

3. The composition of claim 1 wherein the alkyl ester of the unsaturated carboxylic acid is a mixture of lauryl and stearyl methacrylates and the alkyl ester of the olefinically unsaturated phosphonic acid is diethyl isopropylidene phosphonate.

4. The composition of claim 3 wherein the alkyl ester of the unsaturated carboxylic acid is diisooctyl itaconate. 

2. The composition of claim 1 wherein the olefinically unsaturated phosphorus compound is diethyl isopropylidene phosphonate.
 3. The composition of claim 1 wherein the alkyl ester of the unsaturated carboxylic acid is a mixture of lauryl and stearyl methacrylates and the alkyl ester of the olefinically unsaturated phosphonic acid is diethyl isopropylidene phosphonate.
 4. The composition of claim 3 wherein the alkyl ester of the unsaturated carboxylic acid is diisooctyl itaconate. 